Spark plug electrode structure



April 13, 1948. 1'. TOGNOLA 2,439,590

SPARK PLUG ELECTRODE STRUCTURE Filed July 7, 1943 INVENTOR. FIG. 2. By {W ATTORNEY Patented Apr. 13, 1948 UNITED STATES PATENT OFFICE I 2,439,590

SPARK PLUG ELECTRODE STRUCTURE Tullio Tognola, Sidney, N. Y., assignor to Bendix Aviation Corporation, New York, N. Y., a corporation of Delaware Application July '1, 1943, Serial No. 49am This invention relates to ignition apparatus for internal combustion engines or the like and more particularly to spark plugs and parts thereof I It is a well and universally known fact that the electrodes of a spark plug between which the spark or electric arc is created within an engine cylinder are the first elements of a well constructed spark plug to deteriorate from use and to-thereby render the spark plug ineflicient or wholly ineffectiveor inoperative. It is accordingly an object of the present invention to provide a novel electrode structure for a spark plug whereby the useful life of the latter may be materially extended.

Another object of the invention is to provide novel means for restoring to usefulness a deteriorated electrode of a spark plug without ap-' preciably disturbing the remainder of the spark plug structure.

Still another object is to provide a novel method of reconditioning a used electrode in an assembled spark plug or separable unit thereof.

A further object is to provide a novel electrode structure in a spark plug whereby the portion '9 Claims. (Cl. 125-169) ceramics or like materials.

thereof which wears out readily in use may be inexpensivelyreplaced and in such a manner as to restore the original emciency and efl'ectiveness of the spark plug. 7

The above and further objects and novel features of the invention will more fully appear from the following detailed description whe the same is read in connection with the accompanying drawings. It is to be expressly understood, however, that the drawings are for the purpose of illustration only and are not intended as a definition of the limits of the invention, reference for this latter purpose being primarily had to the appended claims. g

In the drawings, wherein like reference characters refer to like parts throughout the several views,

Fig. 1 is an enlarged side elevation, partly in section and with parts broken away, of one, form of spark plug to which the present invention is applicable;

Fig. 2 is a bottom view of the spark plug shown in Fig. l; and.

Figs. 3, 4 and 5 are detail views, partly in section and with parts broken away. showing the center electrode of the spark plug of Fig. 1' in various stages of completion and illustrating the steps inthe novel reconditioning process comprehended by the invention.

The single embodiment of the invention illustrated in the drawings is shown,'-by way of example, as applied to a radio-shielded spark plug The spark plug shown in the drawings comprises a shell it which is provided with external threads H for threaded engagement with an opening in an engine cylinder (not shown). Extending upwardly from shell l0 and formed integrally therewith or secured thereto in any suitable known manner is a shielding barrel I! which, as pointed out above, is not a necessary element of the invention. Suitably mounted in shell I0 and barrel II in any of many well-knownways a is a center electrode assembly comprising a center electrode I! which is insulated from shell i0 by some suitable insulating material, such as mica sleeve i4 and mica washers It. The details of the center electrode assembly may, for example, be of the character disclosed in Tognola Patent No. 2,300,714. r

In the illustrated embodiment, center electrode It comprises a spindle It which is surrounded by mica sleeve l4 and a head or tip which, in turn, consists of a cylindrical portion i1 and a frustro-conical portion It. The latter portion preferably has its conical surface in parallel and spark gap relation to a plurality of bendable prongs it of a ground electrode 20, which is secured in the lower-end of shell l0, preferably in the manner disclosed in Kishbaugh U. S. Patent No, 2,300,730.

During operation of the spark plug described above. the rapid succession of sparks between prongs I 9 and tip portion it of the center electrode under high heat and pressure in'an atmosphere of combustible'vapor causes relatively rapid erosion oi the adjacent surfaces of these parts. Up to a certain extent, this erosion may be partially and satisfactorily corrected by bending the prongs l9 inwardly to insure the proper spark gap. Prior to conception of the present invention, it was the usual practice when this adjustment would'no longer compensate for the wear or erosion to discard the entire spark plug or to at least disassemble and rebuild the entire structure. The novel construction contemplated by the present invention makes it possible to readily and inexpensively recondition such used spark plugs and. render the same substantially as efficient and durable as new structures.

In the process of reconditioning contemplated,

' moved from the shell to permit access to the nose portion of the center electrode assembly. In instances where the erosion of tip I8 is not too severe, it'is only necessary to machine this portion of the electrode to remove the pits and deep blemishes by increasing the angle of the external effected by first machining or turning down the frustro-conical tip it or corresponding portion of other types of electrodes to form a substantially cylindrical stem or post 2|, as illustrated in Fig. 3. A small recess or counter-bore 221sthen drilled in the end of'said stem and the surfaces of said stem and electrode portion l"l are coated with a suitable soldering flux. There-- after, a quantity of solder, such as silver solder, which is preferably in the form of a thin washer 23, is put in place and a new tip member 24 of,

suitable electrode metal is placed over stem 2|. Said member is preferably'cylindrical,as shown in Fig, 4, the same having an external diameter substantially equal to the diameter of head portion I! of the electrode and an internal diameter only slightly larger than the diameter of post 2|. At its outer end, the bore through member 24 is enlarged slightly to form a conical recess 25, as best seen in Fig. 4.

After the parts have been assembled, as illustrated in Fig. 4, the outer end of stem 2! is spun outwardly in the manner illustrated in Fig. 5 to provide a mechanical lock for holding member 24 in place and prevent any possibility of the same coming. loose and dropping out. The tip or nose portion of the electrode is then heated to approximately 1400 F., depending upon the melting point of the solder used. In order to localize the heating and thus avoid damage to the remainder of the electrode assembly, electrical induction heating is employed. This type of heating with a Lepel machine also insures rapid penetration of the heat to the center of the tip assembly. While the assembly is heated, additional solder is put on the en'd of the electrode assembly to fill recess 22 and flow into the bore of member 24 around stem 2i. While the solder, including washer 23, is in melted condition, manual or mechanical pressure is applied with a suitable tool which simultaneously presses member 24 against the surface of tip portion ll and-further .spreads the outer end of stem 2|. The application of the pressure is preferably continued until after the assembly has cooled to a temperature below the melting point of the solder employed. During the application of this pressure, solder from washer 23 is forced into the bore of member 24 around core 2i. Substantially all adjacent surfaces of member 24 and electrode portions l1 and 2i are intimately secured to one another by high heat conductin solder. v

When the assembly has been cooled to room temperature, member 24 is machined or turned down to the same dimensions as the corresponding portion of a new spark plug and the outer course, the tip member 24 may be partially ma- 4 chined before it is secured in place on the center electrode assembly. It will also be understood that the center electrode structure illustrated in Fig. 5 is applicable to new. spark plugs as well as to reconditioned spark plugs. when electrode member 24 becomes worn or eroded, the same may be removed and a new one installed in its place. When the new tip piece 24 has been installed and machined to proper dimensions, a new ground electrode I9. 20 may be se-- cured in position in shell I0. Where the shell is removable from the center electrode assembly or unit, the new ground electrode may be put in at any time.

There is thus provided a spark plug which embodies a novel center electrode structure which may be incorporated either in a new spark plug or in a used one-in the latter case to restore an eroded center electrode to emcient operating condition. Additionally, the invention contemplates a novel structure and a method of constructing the same which facilitate restoration of used or worn out spark plug electrodes without appreciably disturbing the major assemblies of the spark plug structure. The method and novel structure contemplated also reduce to a minimum the operating cost of engines insofar as spark plugs are concerned, without any reduction in operating efficiency.

Although only a single embodiment of the invention is illustrated and described in the foregoing specification, it is to be expressly understood that the invention is not limited thereto. For example, as heretofore pointed out, the invention is applicable to other types of spark plugs having different types of insulation and electrode structures. Various changes may also be made in the design and arrangement of parts illustrated without departing from the spirit and scope of the invention. as will now be understood by those skilled in the art. For a definition of the limits of the invention, reference is had primarily to the appended claims.

What is claimed is:

1. In a spark plug .for internal combustion engines or the like, a center electrode comprising an elongated spindle and a head on said spindle at one end thereof, said head comprising an enlarged portion integral with said spindle, a stem portion integral with said enlarged portion, said stem portion being coaxial with said spindle and at the opposite side of said enlarged portion, a tip member surrounding said stem portion, and means for securing said tip member to said stem portion and said enlarged portion.

2.In a spark plug for internal combustion engines or the like, a center electrode comprising an elongated spindle and a head at one end thereof, said head comprising an enlarged disclike portion integral with said spindle, a stem integral with said disc-like portion and coaxial with said spindle, a tip piece around said stem and butting against said disc-like portion, and

stem and disc-like portion.

3. In a spark plug for internal combustion engines or the like, a center electrode structure comprising an elongated spindle and a head at one end of said spindle, said head comprising an enlarged disc-like portion integral with said spindle, a stem integral with said disc-like portion and extending in the opposite direction from said spindle, a tip piece surrounding said stem, and means including a fusible metal for securing said tip piece to said disc-likeportion and said stem.

fusible, means for securing said tip piece to said 4. In a spark plug for internal combustion engines or the like, a center lectrode structure comprising an elongated spindle and a head at one end of said spindle, said head comprising an enlarged disc-like portion integral with said spindle, a stem integral with said disc-like portion and extending in the opposite direction from said spindle, and a tip piece surrounding said stem, 3, portion of said stem being pressed outwardly into overlapping relation with said tip piece to mechanically lock the latter in position on said structure.

5. In a spark plug for internal combustion engines or the like, a center electrode structure comprising an elongated spindle and a head at one end of said spindle, said head comprising an enlarged disc-like portion integral with said spindle, a stem integral with said disc-like portion and extending in the opposite direction from said spindle, a tip piece surrounding said stem, a portion of said stem being pressed outwardly into overlapping relation with said tip piece to meehanically lock the latter in position on said structure, and fusible means for connecting the adjacent surfaces of said piece and said stem and disc-like portion.

6. A center electrode for a spark plug comprising an elongated spindle, a stem portion coaxial with said spindle, an enlarged disc-like portion between adjacent ends of said spindle and stem and integral therewith, a tip piece having a bore therethrough for receiving said stem, and fusible means for securing said tip piece to said ste and disc-like portions.

'7. A center electrode for a, spark plug comprising an elongated spindle, a stem portion coaxial with said spindle, an enlarged disc-like portion Jacent surfaces 01' said stem Number between adjacent ends of said spindle and stem and integral therewith, a tip piece having a bore therethrough for receiving said stem, and means for securing said .tip piece in position including fusible means'between said tip piece and the adportion and said disclike portion.

8. A center electrode for aspark plug comprising an elongated spindle, a stem portion coaxial with said spindle and having a recess in one end thereof, an enlarged disc-like portion between adjacent ends of said spindle and stem, and a tip piece having a bore therethrough for receiving said stem, the recessed portion of said stem being spun outwardly into locking engage ment with said tip piece.

9. A center electrode for a spark plug comprising an elongated spindle, a stem portion coaxial with said spindle and having a recess in one end thereof, an enlarged disc-like portion between adjacent ends of said spindle and stem, a tip piece having a bore therethrough for receiving said stem, the recessed portion of said stem being spun outwardly into locking engagement with said tip piece, and fusible means for joining said tip piece to said stem and disc-like portion.

TULLIO TOGNOLA.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS 7 Name Date 2,135,240

2,289,676 Paulson July 14, 1942 Paulson Nov, 1, 1938 v 

